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mm/list_lru: make the case where mlru is NULL as unlikely

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In the following memcg_list_lru_alloc() function, mlru here is almost
always NULL, so in most cases this should save a function call, mark mlru
as unlikely to optimize the code, and reusing the mlru for the next
attempt when the tree insertion fails.

        do {
                xas_lock_irqsave(&xas, flags);
                if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
                        xas_store(&xas, mlru);
                        if (!xas_error(&xas))
                                mlru = NULL;
                }
                xas_unlock_irqrestore(&xas, flags);
        } while (xas_nomem(&xas, GFP_KERNEL));
>       if (mlru)
                kfree(mlru);

Link: https://lkml.kernel.org/r/20250227082223.1173847-1-jingxiangzeng.cas@gmail.com
Signed-off-by: Zeng Jingxiang <linuszeng@tencent.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@intel.com/
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Jingxiang Zeng <linuszeng@tencent.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zeng Jingxiang 2025-02-27 16:22:23 +08:00 committed by Andrew Morton
parent f9aad62200
commit b9585a3f3e
1 changed files with 9 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
mm/list_lru.c
View File

@ -510,7 +510,7 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
gfp_t gfp)
{
unsigned long flags;
struct list_lru_memcg *mlru;
struct list_lru_memcg *mlru = NULL;
struct mem_cgroup *pos, *parent;
XA_STATE(xas, &lru->xa, 0);
@ -535,9 +535,11 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
parent = parent_mem_cgroup(pos);
}
mlru = memcg_init_list_lru_one(lru, gfp);
if (!mlru)
return -ENOMEM;
if (!mlru) {
mlru = memcg_init_list_lru_one(lru, gfp);
if (!mlru)
return -ENOMEM;
}
xas_set(&xas, pos->kmemcg_id);
do {
xas_lock_irqsave(&xas, flags);
@ -548,10 +550,11 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
}
xas_unlock_irqrestore(&xas, flags);
} while (xas_nomem(&xas, gfp));
if (mlru)
kfree(mlru);
} while (pos != memcg && !css_is_dying(&pos->css));
if (unlikely(mlru))
kfree(mlru);
return xas_error(&xas);
}
#else